function Stack(){
	this.data = [];
};

Stack.prototype.push = function(element)
{
	this.data[this.data.length] = element;
}

Stack.prototype.pop = function()
{
	if (this.isEmpty())
	{
		return null;
	}
	var temp = this.data[this.data.length - 1];
	delete this.data[this.data.length - 1];
	this.data.length--;
	return temp;
}

Stack.prototype.isEmpty = function()
{
	return (this.data.length == 0);
}

Stack.prototype.peek = function()
{
	return this.data[this.data.length - 1];
}
